The Archbishop of Canterbury, Justin Welby, conducted the private service at the church of St Mary Magdalene in Sandringham, Norfolk.
It is the same church where her late grandmother, Diana, was baptised.
Among the Royals who attended the ceremony were parents - the Duke and Duchess of Cambridge - her brother Prince George, and the Queen.
Meanwhile nine out of ten parents who decide to christen their child say it is an essential foundation to life.
New figures show over two thousand ceremonies take place every week in England.
Canon Dr Sandra Miller, from the Archbishops Council, told Premier: "I think celebration is a great thing, and having parties and coming together as families and friends is fantastic.
"Any occasion that brings together family and friends is a good thing, and people at Christenings are often choosing as God parents people who have been part of their family for a long while, and their saying they're going to be part of the of a family going into the future - so they bring everyone together.
"I think it'll be great for the royal family, and great for so many other babies and their families on this Sunday who are being Christened."
Flowers given by members of the public were given to representatives of East Anglia's Children's Hospices (EACH), where Kate is a patron, who will then take them to hospices in the region.
The Duke and Duchess of Cambridge have asked five people to be godparents to Princess Charlotte, all of whom are friends or family of The Duke and Duchess of Cambridge: Miss Sophie Carter, Mr James Meade, Mr Adam Middleton, The Hon. Laura Fellowes (Prince William's cousin) and Mr Thomas van Straubenzee.
Will and Kate married in Westminster Cathedral in 2011.
